1. Field of the Invention
The present invention relates to a friction agitation joining method for joining metallic joining members, and relates more particularly to a friction agitation joining method for butt joining metallic members to be joined, such as aluminum members or its alloys.
2. Description of the Related Art
Conventionally, as a friction agitation joining method, which is one type of solid-phase joining method, the following method has been proposed. In the method, a joining device 103 as shown in FIG. 3 has been used. The joining device 103 is provided with a column-shaped rotor 130 having a larger diameter and a pin-shaped probe 132 having a smaller diameter. The probe 132 is integrally provided on an end of the rotor 130 so as to protrude along an axis of the rotor 130 and is made of materials harder than that of the members 101, 102 to be joined (hereinafter referred to as "joining members"). While rotating the rotor 130, the probe 132 is inserted into a butted portion of the two members 101, 102. Generally, such insertion of the probe 132 will be performed until an end face 131 of the rotor 130 on which the probe 132 is formed, touches the joining members 101, 102. And then, while the probe 132 is inserted in the abutted portion, the probe 132 is advanced against the joining members 101, 102 along the abutted portion. At a portion of the joining members 101, 102 where the probe 132 contacts and around thereof, the materials of the joining members 101, 102 will be softened by the friction heat generated due to the rotation of the probe 132 and agitated by the probe 132. In accordance with the advancing movement of the probe 132, the softened and agitated materials of the joining members 101, 102 are plastically fluidized to go around the probe 132 and to full up a grove formed behind the probe 132 as it moves by the pressure caused by the advancing movement of the. probe 132. Then, the materials will be cooled and solidified by the immediate loss of such friction heat. This phenomenon will be repeated with the advancing movement of the probe 132, which causes the joining members 101, 102 to be joined.
This friction agitation joining method has advantages in that the materials of metallic joining members are not limited and the deformation of the joining members caused by heat stress is small.
When long joining members are to be joined with their longitudinal edges butted, the butted portion may have gaps in places due to stress of the joining members. In the friction agitation joining method, because filler metals will not be supplied from outside as in melt welding, such as with TIG welding, the materials to be supplied for joining may be insufficient at portions where gaps exist. In this case, the gaps will not be filled up, which cause joining defects, resulting in poor joining.